Wave Interactions As A Seismo Acoustic Source PDF Download
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Author | : Alick C. Kibblewhite |
Publisher | : Springer |
Total Pages | : 259 |
Release | : 2006-04-10 |
Genre | : Science |
ISBN | : 3540493050 |
Download Wave Interactions As a Seismo-acoustic Source Book in PDF, ePub and Kindle
This book gives a comprehensive, theoretical account of the wave-wave interaction process responsible for high acoustic noise levels, including: a geometric description of the interaction mechanism, which provides the basis for a full-wave analysis of the source process, the inclusion of both the monogeneous and inhomogeneous components of the wave-induced pressure field in the analytical description of the source, an examination of the relative contributions of the sum and difference-frequency components of the wave interaction process, the removal of the deep-water assumption of earlier analyses, and the development of an "exact" analytical expression which allows the source function of the wave-induced pressure field to be calculated over the whole frequency-wave number domain.
Author | : T. Akal |
Publisher | : Springer Science & Business Media |
Total Pages | : 898 |
Release | : 2013-03-09 |
Genre | : Science |
ISBN | : 1461322014 |
Download Ocean Seismo-Acoustics Book in PDF, ePub and Kindle
Seafloor investigation has long been a feature of not only seismology but also of acoustics. Indeed it was acoustics that produced depth sounders, giving us the first capability of producing both global and local maps of the seafloor. Subsequently, better instrumentation and techniques led to a clearer, more quantitative picture of the seabed itself, which stimulated new hypotheses such as seafloor spreading through the availability of more reliable data on sediment thickness over ocean basins and other bottom features. Geologists and geophysicists have used both acoustic and seismic methods to study the seabed by considering the propagation of signals arising from both natural seismic events and man-made impulsive sources. Although significant advances have been made in instrumentation, such as long towed geophysical arrays, ai r guns and ocean bot tom seismometers, the pic ture of the seafloor is still far from complete. Underwater acoustics concerns itself today with the phenomena of propagation and noise at frequencies and ranges that require an understanding of acoustic interaction at both of its boundaries, the sea surface and seafloor, over depths ranging from tens to thousands of meters. Much of the earlier higher frequency (>1 kHz) work included the characterization of the seafloor in regimes of reflection coefficients which were empirically derived from surveys. The results of these studies met with only limited success, confined as they were to those areas where survey data existed and lacking a physical understanding of the processes of reflection and scattering.
Author | : J.T. Fokkema |
Publisher | : Elsevier |
Total Pages | : 365 |
Release | : 2013-10-22 |
Genre | : Science |
ISBN | : 1483291200 |
Download Seismic Applications of Acoustic Reciprocity Book in PDF, ePub and Kindle
The seismic applications of the reciprocity theorem developed in this book are partly based on lecture notes and publications from Professor de Hoop. Every student Professor de Hoop has taught knows the egg-shaped figure (affectionately known as "de Hoop's egg") that plays such an important role in his theoretical description of acoustic, electromagnetic and elastodynamic wave phenomena. On the one hand this figure represents the domain for the application of a reciprocity theorem in the analysis of a wavefield and on the other hand it symbolizes the power of a consistent wavefield description of this theorem. The roots of the reciprocity theorem lie in Green's theorem for Laplace's equation and Helmholtz's extension to the wave equation. In 1894, J.W. Strutt, who later became Lord Rayleigh, introduced in his book The Theory of Sound this extension under the name of Helmholtz's theorem. Nowadays it is known as Rayleigh's reciprocity theorem. Progress in seismic data processing requires the knowledge of all the theoretical aspects of the acoustic wave theory. The reciprocity theorem was chosen as the central theme of this book as it constitutes the fundaments of the seismic wave theory. In essence, two states are distinguished in this theorem. These can be completely different, although sharing the same time-invariant domain of application, and they are related via an interaction quantity. The particular choice of the two states determines the acoustic application, in turn making it possible to formulate the seismic experiment in terms of a geological system response to a known source function. In linear system theory, it is well known that the response to a known input function can be written as an integral representation where the impulse response acts as a kernel and operates on the input function. Due to the temporal invariance of the system, this integral representation is of the convolution type. In seismics, the temporal behaviour of the system is dealt with in a similar fashion; however the spatial interaction needs a different approach. The reciprocity theorem handles this interaction by identifying one state with the spatial impulse function, also known as the Green's function, while the other state is connected with the actual source distribution. In general, the resulting integral representation is not a spatial convolution. Moreover, the systematic use of the reciprocity theorem leads to a hierarchical description of the seismic experiment in terms of increasing complexity. Also from an educational point of view this approach provides a hierarchy and the student learns to break down the seismic problem into constituent partial solutions. This book should contribute to the understanding that the reciprocity theorem is a powerful tool in the analysis of the seismic experiment.
Author | : John Holland |
Publisher | : |
Total Pages | : 196 |
Release | : 1987 |
Genre | : Monologues |
ISBN | : |
Download Sound Waves and Their Properties in the Surrounding Media Book in PDF, ePub and Kindle
Author | : A. C. Kibblewhite |
Publisher | : |
Total Pages | : 94 |
Release | : 1984 |
Genre | : Ocean-atmosphere interaction |
ISBN | : |
Download Wave-Wave Interactions, Microseisms, and Infrasonic Ambient Noise in the Ocean Book in PDF, ePub and Kindle
This particular work was initiated following a review of the current literature covering the ambient noise field at very low frequencies. The sparsity of good published data and the continuing interest in low frequency ambient noise have prompted this effort at this time. This report is intended to be the first in a series of contributions to the subject which will be submitted for publication in the near future from reports prepared in recent years at Applied Research Laboratories, The University of Texas (ARL:UT). In this report, correlations of wave climate and ocean induced microseism activity detected by a land-based sensor are examined. The quality of the data, the long term nature of the observations, and a unique property of the geographical region under investigation have helped clarify the role of nonlinear wave-wave interactions in ocean wave and ocean noise processes
Author | : Nori Nakata |
Publisher | : Cambridge University Press |
Total Pages | : 373 |
Release | : 2019-03-21 |
Genre | : Nature |
ISBN | : 1108417086 |
Download Seismic Ambient Noise Book in PDF, ePub and Kindle
A comprehensive overview of seismic ambient noise, covering observations, physical origins, modelling, processing methods and applications in imaging and monitoring.
Author | : Christopher R. Bradley |
Publisher | : |
Total Pages | : 490 |
Release | : 1994 |
Genre | : Microseisms |
ISBN | : |
Download Very Low Frequency Seismo-acoustic Noise Below the Sea Floor (0.2-10 Hz) Book in PDF, ePub and Kindle
Ambient noise in the sea has been observed for over 100 years. Previous studies conclude that the primary source of microseisms is nonlinear interaction of surface gravity waves at the sea surface. Though this source relationship is generally accepted, the actual processes by which the wave generated acoustic noise in the water column couples and propagates to and along the sea floor are not well understood. In this thesis, the sources and propagation of sea floor and sub-sea floor microseismic noise between 0.2 and 10 Hz are investigated. This thesis involves a combination of theoretical, observational and numerical analysis to probe the nature of the microseismic field in the Blake Bahama Basin. Surface waves are the primary mechanism for noise propagation in the crust and fall into two separate groups depending on the relative wavelength/water depth ratio. Asymptotic analysis of the Sommerfeld integral in the complex ray parameter plane shows results that agree with previous findings by Strick (1959) and reveal two fundamental interface wave modes for short wavelength noise propagation in the crust: the Stoneley and pseudo-Rayleigh wave. For ocean sediments, where the shear wave velocity is less than the acoustic wave velocity of water, only the Stoneley interface wave can exist. For well consolidated sediments and basalt, the shear velocity exceeds the acoustic wave velocity of water and the pseudo-Rayleigh wave can also exist. Both interface waves propagate with retrograde elliptic motion at the sea floor and attenuate with depth into the crust, however the pseudo-Rayleigh wave travels along the interface with dispersion and attenuation and "leaks" energy into the water column for a half-space ocean over elastic crust model. For finite depth ocean models, the pseudo-Rayleigh wave is no longer leaky and approaches the Rayleigh wave velocity of the crust. The analysis shows that longer wavelength noise propagates as Rayleigh and Stoneley modes of the ocean+crust waveguide. These long wavelength modes are the fundamental mechanism for long range noise propagation. During the Low Frequency Acoustic Seismic Experiment (LFASE) a four-node, 12- channel borehole array (SEABASS) was deployed in the Blake Bahama Basin off the coast of eastern Florida (DSDP Hole 534B). This experiment is unique and is the first use of a borehole array to measure microseismic noise below the sea floor. Ambient background noise from a one week period is compared between an Ocean Bottom Seismometer (OBS) and SEABASS at sub-bottom depths of 10, 40, 70 and 100 meters below the sea floor. The 0.3 H z microseism peak is found to be nearly invariant with depth and has a power level of 65 and 75 dB rel 1 (nm/ s2)2)/ H z for the vertical and horizontal components respectively. At 100 m depth, the mean microseismic noise levels above 0.7 Hz are 10 dB and 15-20 dB quieter for the vertical and horizontal components respectively. Most of this attenuation occurs in the upper 10 m above 1.0 Hz, however higher modes in the spectra show narrow bandwidth variability in the noise field that is not monotonic with depth. Dispersion calculations show normal mode Stoneley waves below 0.7 Hz and evidence of higher modes above 0.8 Hz. A strong correlation between noise levels in the borehole and local sea state conditions is observed along with clear observation of the nonlinear frequency doubling effect between ocean surface waves and microseisms. Particle motion analysis further verifies that noise propagates through the array as Rayleigh/Stoneley waves. Polarization direction indicates at least two sources; distant westerly swell during quiescent times and local surface waves due to a passing storm. Above 1.0 Hz the LFASE data shows little coherence and displays random polarization. Because of this, we believe scattered energy is a significant component of the noise field in the Blake Bahama Basin. A fully 3-D finite difference algorithm is used to model both surface and volume heterogeneities in the ocean crust. Numerical modeling of wave propagation for hard and soft bottom environments shows that heterogeneities on the order of a seismic wavelength radiate energy into the water column and convert acoustic waves in the water into small wavelength Stoneley waves observed at the borehole. Sea floor roughness is the most important elastic scattering feature of the ocean crust. Comparisons of 2D and 3D rough sea floor models show that out-of-plane effects necessitate the use of 3D methods. The out-of-plane energy that is present in the LFASE data comes from either heterogeneities in the source field (i.e. mixed gravity wave directions) or, equally likely, scattering of the source field from surface or volume heterogeneities in the sea floor.
Author | : Michael J Buckingham |
Publisher | : World Scientific |
Total Pages | : 512 |
Release | : 1996-01-11 |
Genre | : |
ISBN | : 981453188X |
Download Sea Surface Sound '94 - Proceedings Of The Iii International Meeting On Natural Physical Processes Related To Sea Surface Sound Book in PDF, ePub and Kindle
Understanding and constructively using natural sound in the ocean has become of prime importance with the shift of emphasis to protecting the environment and exercising responsible global resource management which has followed the end of the Cold War. Especially now that we realise that marine mammals and other inhabitants of the oceans are threatened by our acoustic pollution of their environment, the use of natural sound as a non-intrusive remote sensing probe has become particularly germane. This was the first meeting on the subject since the fall of Soviet-Western barriers, and the proceedings include significant work from premier researchers in the former Soviet Union. It was also the first meeting which specifically addressed the new and exciting idea of using natural sound in applications for monitoring the marine environment. The proceedings include a number of papers on various aspects of this topic. Further new work on the basic physics of sound production and propagation is also included. This volume includes leading-edge work from the foremost researchers in the field, including Bill Carey, Lawrence Crum, Nikolai Dubrovskii, David Farmer, Brian Kerman, Bill Kuperman, Michael Longuet-Higgins, Hank Medwin, Ken Melville, A Prosperetti and many others.
Author | : United States. Environmental Science Services Administration |
Publisher | : |
Total Pages | : 462 |
Release | : 1968 |
Genre | : Gravity waves |
ISBN | : |
Download Acoustic-gravity Waves in the Atmosphere Book in PDF, ePub and Kindle
Author | : Thomas Neighbors |
Publisher | : Elsevier |
Total Pages | : 982 |
Release | : 2017-01-19 |
Genre | : Science |
ISBN | : 0128112476 |
Download Applied Underwater Acoustics Book in PDF, ePub and Kindle
Applied Underwater Acoustics meets the needs of scientists and engineers working in underwater acoustics and graduate students solving problems in, and preparing theses on, topics in underwater acoustics. The book is structured to provide the basis for rapidly assimilating the essential underwater acoustic knowledge base for practical application to daily research and analysis. Each chapter of the book is self-supporting and focuses on a single topic and its relation to underwater acoustics. The chapters start with a brief description of the topic’s physical background, necessary definitions, and a short description of the applications, along with a roadmap to the chapter. The subtopics covered within individual subchapters include most frequently used equations that describe the topic. Equations are not derived, rather, assumptions behind equations and limitations on the applications of each equation are emphasized. Figures, tables, and illustrations related to the sub-topic are presented in an easy-to-use manner, and examples on the use of the equations, including appropriate figures and tables are also included. Provides a complete and up-to-date treatment of all major subjects of underwater acoustics Presents chapters written by recognized experts in their individual field Covers the fundamental knowledge scientists and engineers need to solve problems in underwater acoustics Illuminates, in shorter sub-chapters, the modern applications of underwater acoustics that are described in worked examples Demands no prior knowledge of underwater acoustics, and the physical principles and mathematics are designed to be readily understood by scientists, engineers, and graduate students of underwater acoustics Includes a comprehensive list of literature references for each chapter